[S35]: Epigenetic regulation of inhibition is required for myelination

receptors plays an important role in myelination. In keeping with this, expression of the laminin alpha2 chain has been reported on axons at the time ofmyelination, and abnormalities of CNS myelination have been described in mice with mutant laminin alpha2 (dy/dy mice). Laminins are recognised by the alpha6beta1 integrin, and I will describe experiments using expression of dominant negative integrins in transgenicmice to examine the role of this receptor in vivo. The results suggest that beta1 integrin is dispensible for myelination in the CNS. However, parallel experiments using myelinating co-cultures show the opposite, and reveal that the timing of integrin loss is critical; prior to myelination no effect is seen but inhibition using antibodies blocks myelination if started after the initiation of the axo-glial interaction. They also show that loss of signalling by the mitogen PDGF is also required for myelination. Together, these results suggest that integrin/ growth factor interactions are important during myelination, with the timing of signalling being an important part of the regulatory process.